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From Jeff Trawick <traw...@attglobal.net>
Subject Re: Release 2.0.36
Date Fri, 26 Apr 2002 03:12:22 GMT
Greg Ames <gregames@apache.org> writes:

> The other is a sendfile assert that we've seen intermittently for a long time. 
> Jeff thinks the FreeBSD kernel is giving us a return value of 0 with no bytes
> sent.  I think we might be passing a length or an offset that's too big, perhaps
> when the site is updated after we stat() the file.  I plan to write traps to
> test both theories.

Here's what I think in a little more detail:

[I suspect that] Both FreeBSD and Linux sendfile() will return 0 in
some conditions where it sends no bytes.  The conditions?  Bogus
offset/length combination.  I just verified that on Linux I get return
code 0 from sendfile() when asking it to send 8192 bytes starting at
offset 999999999 in a file that is much smaller than that.  The file
offset was updated to 999999999.  (It seems that sendfile picks up
some semantics from sparse file support in seek-type operations.)

Why would we give sendfile a bogus offset/length combination?

a couple of possible reasons:

a) like you said, the file size could change during the request (a
   definite problem)
b) we bungle the processing somehow and come up with a bogus file
   bucket

-- 
Jeff Trawick | trawick@attglobal.net
Born in Roswell... married an alien...

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